Oracle stored procedure with case when in the where cause - oracle

Question

The following stored procedure complied with errors. It seems the errors are in the case statement in the where cause. How do I fix it?
create or replace PROCEDURE APPEND_HIST_TBLS_PROC AS
CurTerm varchar2(4) := '1222';
PS_ACAD_PROG_HISTORY varchar2(35) := 'PS_ACAD_PROG_HISTORY_' || CurTerm;
Begin
execute immediate 'insert into ' || PS_ACAD_PROG_HISTORY
|| '(select sysdate as date_created,
EFFDT,
ADMIT_TERM,
EXP_GRAD_TERM,
CAMPUS
from ERP_ACAD
where CASE WHEN SUBSTR(ADMIT_TERM,4,1)= '6' THEN SUBSTR(ADMIT_TERM,1,3) || '9' ELSE ADMIT_TERM END = '||CurTerm ||'
)';
END APPEND_HIST_TBLS_PROC;

Answer 1

Dynamic SQL is difficult to maintain and debug. The fact that procedure compiled successfully tells nothing about the dynamic statement itself - it just says that there were no errors in the procedure "as is".
It is a good habit to compose the statement and store it into a local variable and then display its contents; once you verify it is OK, then execute it.
Also, as you have to escape single quotes (sometimes it becomes nasty, with several consecutive single quotes which do what you need), use the q-quoting mechanism which lets you write "normal" statements (single quotes really are single, then).
Something like this:
SQL> CREATE OR REPLACE PROCEDURE append_hist_tbls_proc
2 AS
3 curterm VARCHAR2 (4) := '1222';
4 ps_acad_prog_history VARCHAR2 (35) := 'PS_ACAD_PROG_HISTORY_' || curterm;
5 l_str VARCHAR2 (4000);
6 BEGIN
7 -- Compose the INSERT statement into a VARCHAR2 local variable so that you'd be able
8 -- to check whether you did it right or not.
9 -- Use the q-quoting mechanism as it helps with consecutive single quotes issues
10 l_str :=
11 'INSERT INTO '
12 || ps_acad_prog_history
13 || q'[ SELECT sysdate as date_created,
14 effdt,
15 admit_term,
16 exp_grad_term,
17 campus
18 FROM erp_acad
19 WHERE CASE WHEN SUBSTR(admit_term, 4, 1) = '6' THEN
20 SUBSTR(admit_term, 1, 3) || '9'
21 ELSE ADMIT_TERM
22 END = ]'
23 || curterm;
24
25 -- FIRST check the command you're about to execute
26 DBMS_OUTPUT.put_line (l_str);
27
28 -- When you verified that it is correct, then comment DBMS_OUTPUT.PUT_LINE call
29 -- and uncomment EXECUTE IMMEDIATE
30 -- EXECUTE IMMEDIATE l_str;
31 END append_hist_tbls_proc;
32 /
Procedure created.
Let's try it:
SQL> SET SERVEROUTPUT ON
SQL> EXEC append_hist_tbls_proc;
INSERT INTO PS_ACAD_PROG_HISTORY_1222 SELECT sysdate as date_created,
effdt,
admit_term,
exp_grad_term,
campus
FROM erp_acad
WHERE CASE WHEN SUBSTR(admit_term, 4, 1) = '6'
THEN
SUBSTR(admit_term, 1, 3) || '9'
ELSE
ADMIT_TERM
END = 1222
PL/SQL procedure successfully completed.
SQL>
Output looks ugly (that's the price of having it pretty in the procedure), but - if you format it - it looks like this:
INSERT INTO PS_ACAD_PROG_HISTORY_1222
SELECT SYSDATE AS date_created,
effdt,
admit_term,
exp_grad_term,
campus
FROM erp_acad
WHERE CASE
WHEN SUBSTR (admit_term, 4, 1) = '6'
THEN
SUBSTR (admit_term, 1, 3) || '9'
ELSE
ADMIT_TERM
END = 1222
So, if you can really execute it (I can't, I don't have your tables), then uncomment execute immediate and use the procedure. Otherwise, fix the statement.

Answer 2

Seems like an issue with quoting. Have you tried this:
create or replace PROCEDURE APPEND_HIST_TBLS_PROC AS
CurTerm varchar2(4) := '1222';
PS_ACAD_PROG_HISTORY varchar2(35) := 'PS_ACAD_PROG_HISTORY_' || CurTerm;
Begin
execute immediate 'insert into ' || PS_ACAD_PROG_HISTORY
|| '(select sysdate as date_created,
EFFDT,
ADMIT_TERM,
EXP_GRAD_TERM,
CAMPUS
from ERP_ACAD
where CASE WHEN SUBSTR(ADMIT_TERM,4,1)= ''6''
THEN CONCAT(SUBSTR(ADMIT_TERM,1,3), ''9'') ELSE ADMIT_TERM END = '||CurTerm ||'
)';
END APPEND_HIST_TBLS_PROC;
Also used CONCAT instead of double pipe assuming you want to append 9 at the end of sub string of admin_term.
Really depends on your data and the logic you are trying to implement. This procedure should now compile but whether it achieves the desired result - depends on the logic you are trying to implement here.